What is the advantage of having a single instance when using the Singleton standard in web development?

Question

Researching a little more about Singleton I found some comments in favor and against the use of this approach.

But I still doubt the usefulness of instantiating a single instance of a class (and doing it globally) in a web development scenario, where we should load this object between sessions.

In short my question would be, what advantage or what would make a programmer choose Singleton in a web development scenario, since there is no way to create global objects between sessions. Another approach would be to instantiate a class at login and load it into the global variables between pages.

Here in this specific scenario I refer to web development using php for example.

Answer 1

The Singleton standard helps increase system performance in a web application, especially in connections to external databases or sources.

Instead of creating a connection each time with the database, it will be created once for every web instance (while not returning to screen), reducing the query time and the number of connections.